Two heads are better than one, so the first task in many startups is finding a co-founder or two. You need to find the skills or experience you don’t have in business, technology or money. The first question I usually get is what percent of the company or equity is that person worth? Giving a co-founder a salary won’t get you the “fire in the belly” you want.

The default answer, to keep peace in the family, is to split everything equally, but that’s a terrible answer, since now no one is in control, and startups need a clear leader. The next default of waiting until later is equally bad, since partners who bow out early will still expect an equal share of that first billion you make later.

Now comes the reality check. Just because it was your idea doesn’t mean you “deserve” 90 percent of the equity. The value in a startup is all about tangible results, so there is no equity value in the idea alone. Thus the real discussion must start with who will be doing the work, providing the funding and delivering results. Each co-founder should get equity for value, based on these key variables:

Lived a key role in a previous startup. Building a new business is quite different from an executive role in a mature company, so people from these backgrounds are often a liability. Value is embodied in previous success with investors, proven problem-solving ability, and having built and executed a business plan with minimal resources.

Experience and connections in your business area. Textbook knowledge and academic degrees don’t count here. Value factors include your related product breadth and depth, relationships with thought leaders, key vendors and large potential customers. Building the product may be the easy part of your startup challenge.

Key to required patents or trade secrets. In many cases, one of the co-founders may bring some work in progress that can be patented, trademarked or copyrighted. Your idea is not intellectual property yet, so it has no inherent value. Every previous experience filing and winning a patent is a rare and valuable asset.

Level of responsibility and time allocated. Co-founders only able to work part-time, with responsibility and major income sources elsewhere, don’t carry the same risk as others with more operational responsibility. Less dependence or startup success, or more cash compensation, generally means less equity assigned.

Amount of venture funding provided. Investors may not be called co-founders, but they always get equity, commensurate with their share of the total costs anticipated, or share of the current valuation. The challenge is for real co-founders to keep their equity percentage above 50 percent, or they effectively lose control of operational decisions.

If none of these five items is a clear differentiator in your case, a logical approach would be to assign each an equal weight of 20 percent of the total, and partition the total equity based on each co-founder’s correlation to each variable. A friend or family investor thus might get 20 percent of the equity, even with no business activity contribution.

Because these considerations can be quite complex, very emotional and have long-term implications, smart entrepreneurs don’t hesitate to get some legal advice at this early stage, in drawing up an agreement document to be signed by each of the co-founders. Obviously it should be amended later, as roles are more clearly defined, and execution proceeds.

Even with an agreed initial equity split, it’s smart to have founder’s stock actually issued or vested over a period of at least two years, on a month-by-month basis. That way, if one of the partners disappears, or their role changes, a portion of the equity can be re-captured and reallocated to the other members. Other common terms, like the right to re-purchase, should be investigated.

In all cases, roles and titles should be clear, but not necessarily tied to any given percent of equity. In other words, the CEO need not be top equity owner, but should be the one with the most business skill and experience. The CTO of many technical startups was the original founder. The CFO may have a major financial background, but might be a minority owner.

Of course, all co-founders need to remember that allocated percentages will be diluted as angel and venture capital investors are brought in. Keep your wits about you to make sure that dilution is done equitably and evenly. Naïve cofounders have found themselves squeezed out in some recent cases, including Facebook.

But don’t get greedy. It’s the power of the whole team that makes the business.